[Lazarus] Proposal for TControl.DoDock patch

[Michael Van Canneyt]

On Mon, 5 Apr 2010, Hans-Peter Diettrich wrote:

> Michael Van Canneyt schrieb:
>
>> I have been thinking about layout managers. I think that this should be an 
>> add-on
>> to the currently existing layouting (to preserve delphi compatibility): I 
>> imagine a component that one drops on a form. One sets the 'target' control 
>> (control whose children should be managed) and some properties.
>
> I imagine a Layout property for TWinControls, or an intermediate layer, that 
> is initialized to the Delphi compatible manager. That property then can be 
> assigned any other layout manager.

That is the same as what I am saying, only the arrow points in the opposite
direction. I want to avoid this extra TWinControl property.

>> The only thing I am unsure about is whether TControl should be made 
>> TLayout-aware.
>> As far as I understand, a layouter only needs to be able to handle 
>> rectangles,
>> within some restrictions (some callbacks to get min/max rectangles). It 
>> need not know anything about TControl or it's properties, and as such could
>> be implemented totally independent of the LCL.
>
> The layout should take into account the standard TControl properties, 
> including alignment, constraints and anchors. It also should use the layout 
> managers of child controls, for forward/backward transfer of autosize 
> information.

This is *exactly* what I want to avoid.

- Either one uses the 'ordinary' delphi properties, and only those.

- Or one uses layouters.

But not a mixture of both, which will be a source of implementation/usage
problems and confusion. Keep it simple.

Once this split works correctly, you can always later try to create a 
TLayout descendent which tries to mimic Delphi behaviour, taking into 
account all TControl/TWincontrol properties; Then remove all old code
and insert the new layouter.

In my opinion, this approach guarantees has a bigger chance of success 
than immediatly trying to do everything at once...

Michael.